But there are still those who do, and Top Rank's Bob Arum said it is not out of the question for September 2014.

But the question is, if the fight happens, could Pacquiao be competitive with Mayweather? At one stage three or four years ago, they were the unquestioned No. 1 and unquestioned No. 2 fighters in the world, in whichever order you wished to rank them. I have long believed Mayweather to be the best fighter in the world, and haven't wavered from that belief, but I would still rather see it decided in the ring.

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Floyd Mayweather Jr. (Getty Images)

Pacquiao has to beat Brandon Rios on Saturday (Sunday in Macau) in order for there to be even the slightest glimmer of hope for the bout to happen. But if it were to be signed, Pacquiao trainer Freddie Roach believes the Pacman could pull it off.

Rios trainer Robert Garcia has flip-flopped on the issue.

"Three or four years ago, when Manny was knocking all those people out and looking like a monster, I think he would have beaten Mayweather," Garcia said. "But not now, though. I think Mayweather would beat him now."

Roach, not surprisingly, feels differently. He's under no illusions and knows it would be a hard fight, but said he thinks Pacquiao would win.

"Mayweather is I think slipping a little bit, with his age and so forth," Roach said. "He can't move like he used to. He doesn't use his legs like he used to. He doesn't have the movement. He's not as fluid. He stays on the ropes a lot more. He exchanges a lot more. I think that would benefit Manny Pacquiao in a fight.

"Obviously, Mayweather is very good at what he does. I'm not saying that would be an easy fight. We'd have to come up with a great game plan. We'd have to really stick to it to win that fight. He has some flaws. Nobody is perfect out there. If we could draw those flaws out and take advantage of them, we'd be in a good spot. I still pick Manny to win that fight."

Roach is expecting a big Pacquiao win on Saturday at CotaiArena for one simple reason: He knows Pacquiao knows he desperately needs it to remain regarded as one of the world's elite boxers.

"Everybody here would like to see that happen sooner rather than later, but to get that fight, Manny knows he needs to be impressive in this fight," Roach said. "That's why I am so confident he will be impressive in this fight."